Nickel-plating



UNITED srAres PATENT OF E- EDMUND n. TODD, or minnow, mm winnrs R. xme, or nnwaax, new .mnsEY,

ASSIGNOBS 'I'O HANSON & VAN COMPANY, OFJTE'WABK, NEW JER- SEY, A. CORPORATION OF NEW JERSEY.

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1,352,328. No Drawing Appllcatlon filled December To all whom it may concern:

Be'i known that we, EMU U'N. Tom) and Wnmrs R. KING, both'citizens of the United States, residin at Milburn, in the county of Essex and tate of New Jersey, and Newark, in the county of Essex and State of New Jersey, respectively, have inveitted certain new and useful Improvements in Nickel-Platin', of which the following is a full and 0 car specification.

Our invention relates in general to the electro-deposition of nickel and contemplates certain improvements in the bath and the process of electro plating, as well as certain improved qualities in the character of the deposit.

In the electro-deposition of metals maniy expedients are employed, such' as the a dition of speciallagents' to the bath, special adjustment of current densities and other electrical relations and special manipulation of the cathode, to secure a certain character of deposit or to achieve some-improvement in the process of electroplating. In many cases the theory underlyingthese special operations or conditions is not understood, but those skilled in the art apply them successfully. In the art of nickel plating, there have been many attempts to secure improvements in the structure and surface characteristics of the deposit, andto reduce the time required for a given thickness of the plating. It has also been sought to increase the thickness of uniformdeposit possible, which under. thepresent known methods is quite limited. Beyond a given'thickness, the surface 'becoines irregular and increasingly so as the deposit is continued. A further disadvantage in the nickel plating as practised is the requirement of bufling-the plated surface to secure thebright, mirror-like polish which is desired. This bufling process requires the previous deposit of an excess of the metal to allow for loss in bufiing, and the bufling operation itself involves a considerable item v of'time and expense-which has heretofore been unavoidable. Furthermore, the bufiing is extremely difiicult in cases of heavy relief surface, inaccessible to the bufiing material.

' Qur invention ha's for its object reduce Specification of Letters Patent.

2a, 1014, Serial No. 879,312. Rama Serial no. 358,127.

ited metal.

ing operation and upon the character of thedeposit obtained. In the case of a magnetic metal, such as nickel, we assume I etic lines of force proceeding from the po arized cathode cause an unsat .lsfactory disposition of the nickel ions as adhesion with the cathode surface only at .deposit .is the result.

Patented SeptI'1'L-1Q20.

February '12, 1920. I

the time required for electroplating nickel, to reducethe voltage necessary, to enable the. depos1t of a substantially uniform deposlt of much greater thickness than heretofore possible, and to gain certain important improvements in the internal structure of the deposit as well as certain improvements 111 the surface characteristics of the depos- In practising our invention we proceed upon the assumed theory that polarization has an important bearing upon the platthat the ma they arriveupon the cathode surface, which d1spos1t1on results in a tendency of the metal to stand out from the cathode and build up a structure which isthereforein minute points. Furthermore, our theory assumes that under the ordinary practice with a polarized cathode the particles of metal rapidly build outward upon the multiplicity of minute projections due to the repelling posited would also appear to explain the rapid growth of irregularities upon the surface under ordinary plating conditions which imposes a limit upon the permissible .thickness of the coating. According to our.

theory of operation, the polarization of the electrode is greatly reduced, if not altogether eliminated, and the result is that the particles of the magnetic material are now not repelled by the magnetic lines of force from the cathode and are able to attach themselves closely and compactly to the cathode and to themselves, so that an ex-. tremely hard, dense and compact mass of Furthermore the outersurfaceds flatter and not broken up by the minute spaces between laterally adjacent particles, so that an even smooth and 7 influence of the polarization, and contact mirror-like surface, free from perceptible granulation or facets and havingthe appearance of fused metal is maintained from the begining right straight through to the conclusion of the electroplating operation. This mirror-like surface maintains an exceedingly uniform exposure of cathode surface to the ions with consequent uniformity of current density and distribution of metal as the deposit grows.

roduce minute outstandin projections ing thus minimized the platin is enabled to continue for an almost inde nite period without the objectionable. appearance of warts, and other irregularities in the sur-- face. 'Not only is an'extremely hard, dense Y structure of metal secured, but at the same platin time an astonishingly smooth and mirror-like I finest possible bufiing. This mirror-like surface is microscopic in its structure, as even a frosted surface when subjected to the operation under our invention is repro uced with the same mirror-like gloss. The metal ofthe deposit displays much higher mechanical strength. and tenacity than that obtained by the ordinary plating,

and no matter where a fracture is made, the cleavage surface itself presents the same mirror-like character.

The polarization according to the theory assumed b us, is reduced or eliminated by the use 0 an addition agent in the bath. Whlle, of course, there may be other specific re-agents which will operate under the principles of our invention and produce the de-Y sired results, we may mention, as an example, one which has given hi hly satisfactory results in practice and which may, therefore be regarded as a representative ofa class of materialsv suitable for this purpose. The

substance which we have reference to is contained in the material known in the market as gum tragacanth and while we are aware that this material contains soluble andv insolublesubstances of which the soluble portion possesses the desired substance for the correction of polarization, we find it not worth whlle toseparate'the ingredient but usually employ the gum tragacanth itself withoutprevious separation, and herein designate the agent as "gum tragacanth without meanlng thereby to limit the invention. to

i the use of the entiresubstance. It is also to be understood that the invention is not The tendency to limited tothis specific example. of the agent employed as any other substance per forming the same functions will, of course, be embraced within the broad scope of our invention.

With regard to the manner in which the gum tragacanth effects the reduction or elimination of polarization it is, of course, unnecessary to make exact-determination, as we believe it to be broadly new to utilize a polarization corrective in connection with the electrodeposition of a'magnetic metal in the manner and for the purposes herein described. We may state, however, that in practice we find that the use of gum tragacanth results in the-reduction or elimination of the adhesion of hydrogen bubbles to the cathode surface. This fact alone, may, in

itself, account for the improvements obtained, under the theor that the adhesion of hydrogen bubbles-to t e cathode causes the polarization; or the absence of mechanical obstruction} caused by the hydrogen bubbles ma itself explain the lmpro'vements noted. it may be that the result is due in part to each of the conditions. The fact re, mains that when the gum tragacanth is used in the bath we gain a hard, dense, firmly coherent and homogeneous coating with bright, mirror-like surface, and find that the plating goes faster and requires less voltage. Another peculiar fact is that when the gum tra acanth is employed current densities well in excess of those usually considered permissible canbe employed without burning. the deposit,-resulting in an increased deposit with a lower voltage. The mechanical strength of the. deposit is better. when low voltage is employed. The same material used as an addition agent to an electroplating bath for non-magnetic metals does not appear to have the same effect as when used .in connection with the plating of magnetic metals, such as nickel.

We may state, as an example of a nickel plating bath according to our invention the following: 12 ounces of sulfate of nickel and ammonium in 1 gallon of water, and for each gallonof this solution, 1/15 ounce of gum tragacanth. It will be understood that the exact proportions are subject to considerable variation without departure from the principles of the invention, and the proportions herein stated are only illustrative.

the proportions stated: 12 ounces sulfate of nickel and ammonium, 1/15 ounce of gum tragacanth and one gallon of water.

4. The process of electrodepositing magnetic metal which comprises passing an elec-- tric current through an electrolyte having a composition such as to keep a substantially unpolarized condition at the cathode.

5. The process of electrodepositing magnetic metal which comprises passing an electric current through an electrolyte having a composition such as to keep the cathode free: from hydrogen bubbles.

6. An electrodeposit of magnetic metal having a hard, dense, firmly coherent internal structure and a bright mirror-like outer surface resembling that of buffed metal entirely free from perceptible granulation, said properties being independent of the initial surface upon which the deposit is pro duced.

7. An electrolytical deposit of nickel having a hard,- dense, firmly coherent internal structure, and a continuous outer surface, free from perceptible granuLation,'-having the appearance of fused metal, said properties being independent of the initial surface upon which the deposit is produced.

8. Electrolytic nickel having the qualifications of great hardness and density, a

firmly coherent internal structure, continuity' of outer surface, free from perceptible granulation both on the surface and throughout the mass, and having the appearance of fused metal.

EDMUND N; TODD. Witnesses:

R. B. Fox, W. L. D. BEDELL.

WILLIS R. IxING.

'Witnesses:

S..A. PEoKENs, R. D. FOSTER. 

